Thermocouple operated electromagnet



Dec. 21, 1943. 11m/m51. 2,337,140l

THERMOCOUPLE OPERATED ELECTROMAGNET Original Filed June 16, 19157 2 Sheets-Sheet 1 DQC. 21, 1943. T, A, WETZEL 2,337,140

THERMOGOUPLE OPERATED ELEGTROMAGNET Original Filed June l5, 1937 2 SheetS--Shet 2 2/0 HHHMHIII hum i Patented Dec. 2.1, 1943 THERMOCOUPLE OPERATED ELECTRO- MAGNET Theodore A. Wetzel, Milwaukee, Wis., asslgnor to Milwaukee Gas Specialty Company, Milwaukee, Wis., a corporation of Wisconsin Original application June 16, 1937, Serial No.

148,495, now Patent No. 2,267,775, dated December 30, 1941. Divided and this application November 21, 1941, Serial No. 419,993

3 Claims.

This invention relates to improvements in thermocouple operated electromagnets, and haspan ticular reference to improvements inl thermocouple `operated electromagnets for controlling the supply of gaseous fuel to gas burners and the like.

The present application is a division of my copending application Serial No. 148,495, filed June- 16, 1937, now Patent No. 2,267,775.

In its preferred embodiment, the thermocouple operated electromagnet of the present invention comprises an -electromagnet having a magnet frame and a coil. The main burner is provided with a pilot burner for lighting the same, and a thermocouple provided with a hot junction responsive to the heat of the pilot flame is connected to the coil of the electromagnet. The heat of the pilot flame generates a thermoelectric current in the thermocouple, and this thermoelectric current energizes the electromagnet. The electromagnet has an armature which acts to close and hold closed a circuit for an electrically operated valve in the gas supply pipe for the main burner when the electromagnet is energized by the thermoelectric current generated by the heat oi.' the pilot name.

Closing of the circuit for the electrically operated valve opens this valve to set up and maintain the desired supply of gaseous fuel to the main burner so long as the pilot burner is lighted. If the pilot burner is extinguished, the thermoelectric current ceases, and the electrically operated valve operates to closed position to "shut off the supply of gaseous fuel to the main burner.

A thermoelectric current generated by the heat of a pilot flame' has heretofore been used to control an electrically operated valve in the gaseous fuel supply line for the main burner independently of an auxiliary source of current such as house current or battery, but heretofore the thermoelectric switches have usually been operable only to hold the circuit for'the electrically operated valve closed and have been incapable of operating the switch to close said circuit by means of the relatively weak thermoelectric current produced by the heat of the pilot flame. As a result, resetting devices have been required for resetting the thermoelectric vswitch to closed position.

These resetting devices usually move the armature into contact with the magnet frame of the electromagnet, and, simultaneously, the switch contact means to closed position. ting device is operated to close the thermoelectric switch and thereby the circuit for the electrically operated valve in the fuel supply line, the electrisible explosion when a'ame is applied to light the pilot burner, and also the possibility of asphyxiation.

One of the main objects of the present invention is to provide a thermoelectric switch which not only is adapted to be held closed by a relatively weak thermoelectric current, but is also adapted to be actuated to closed position by such a current without resetting devices or other auxiliary means for closing. the switch.

It is also an object of the invention to provide an improved reaction spring and armature assembly for securing in a thermoelectric switch operated by a relatively weak thermoelectric current not only the desired operation as above set forth, but also a mechanical snap action which will produce a sharp, clean interruption of the current in the c-ircuit controlled bythe thermoelectric switch.

It is to be understood, however, that the thermoelectric switch of the present invention is not limited to use with circuits requiring a snap action or sharp, clean interruption of the current, but may be employed with the so-called locking circuits which incorporate auxiliary contacts to relieve the switch contacts of their initial load.

Another object of the invention is to provide means for adjusting the spring reaction member for the purpose of adjusting the action of the armature and contact member carried thereby in order to vary the time "off after the pilot flame is extinguished.

Another object is to provide an armature assembly which, if the switch is jolted or dropped,

prevents disengagement of the switch contacts.

Further objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which: 'l

Figure 1 is a front elevational view` of a form of thermoelectric switch embodying the present invention;

If the resetr Figure 2 is a vertical section taken on the line 2--2 of Figure 1;

Figure 3 is a horizontal section taken on the line 3 3 of Figure 2;

Figure 4 is a vertical section taken on the line 4-4 of Figure 2;

Figure 5. is a fragmentary view showing the reaction spring member and amature system employed in the embodiment of the invention shown in Figures l to 4l, inclusive; and

Figure 6 is a fragmentary sectional View through the terminal member for the leads of the therrnocouple.

'I'he form of instrument shown in Figures 1 to 5, inclusive, comprises a thermoelectric switch base |36 and a metal box |8| secured thereto by bolt means at |82.

The U-shaped magnet |83 is secured at it to one side of the box iBI. One end of the coil l is electrically connected to the box |8| at |35, and the opposite end of the coil is electrically connected to a terminal plug |81. The plug |87 is insulated from the sleeve |88 by insulation at |89. The plug |87 has an upwardly extending reduced stem which passes up through reenforcing washers 9| on opposite sides of the adjacent end of the ribbon-like member forming the coil |85, and is riveted over at 692. Insulation is provided at I9il between the sleeve IBB and the connected end of the coil |35.

The thermocouple terminal comprises a terminal member E93 xed on the bared end of the thermocouple lead wire I9@ (Figure 6), and a v terminal member |95 surrounds and makesI contact with the thermocouple lead tube |36. The lead wire |95 and lead tube |96 are insulated from each other at |97, and the terminal member |93 is insulated from the terminal member |95 at |98. The insulation at |98 and terminal member ii are interlocked at |99, and the union or coupling member 20@ binds the parts rmly together with the conical tip of the terminal member id@ in good electrical contact with the -corresizionding seat in the plug i8? and with the lead wire connected to one end oi? the coil |85 and the lead tube |96 connected to the other end of the coil through the box mi.

A quick detachable connection is thus provided between the leads of the thermocouple and the coil |85 of the electromagnet. 'I'he thermocouple leads are disconnected from and connected to the coil terminal by the simple expedient of removing and applying the union or coupling member 20d.

The threaded Shanks of contacts 235 and 226 have threaded engagement with metallic connector pieces 2M mounted upon and secured at 2li@ to insulating terminal blocks 299. These blocks 2% are secured at 2| il over openings 2li in the opposite side walls of the box ii. Each connector piece 2t? has a terminal screw 2id in threaded engagement therewith for connecting the circuit conductors to the connector pieces, and thereby to the contacts 2M and 2M, resoectively. One of the circuit conductors is shown at it' and the other circuit conductor is shown at 23' in Figure l, the conductor i6' being connected to the terminal screw 2id for the contact 225, and the conductor 23 being connected to the terminal screw 2id for the opposite contact 2%.

The contact arm 22d, which carries the contact member 22|. is secured at 222 to the insulating member 223. This insulating member in turn is secured at 22d-to the armature arm 225. The contact arm 228 is connected by a conductor 22 to a connector piece 22T mounted on an insulating terminal block 228 at the front of the box ii. The connector piece 227 is electrically connected to an externally disposed connector piece 23@ (Figure l) which is provided with a terminal screw 23| for connecting a lead 'supporting and guide pins 2Mo., as Will be clear from Figures 2, 4, and 5 of the drawings, and tends to force the armature assembly clockwise (Figure 4) about the fulcrum 2&2 to engage contact 22| with contact 206when the coil |25 is deenergized. When the coil is energized, the magnet |83 pulls the armature to the minimum gap position toward the pole faces of the magnet, and thereby moves the contact 22| out of engagement with the contact 20o and into engagement with the Contact 25, and holds the same in this position as long as the pilot iiame is burning.

The sides of the spring member Zihave slots 2&6 in which lugs 261 on the armature arm 225 engage to interlock the armature arm and spring reaction member against relative longitudinal movement. At its lower end, the spring reaction member 246 bears against the inner pointed end of an abutment member in the form of a screw 256 threaded through the adjacent side wall'of the box |8i. The screw 250 is adjustable to adjust the tension of the spring member 25H and, thereby, the time 01T, after the pilot iiame is extinguished. The armature 2d! is shown in Figure 4 in minimum gap position relative to the pole faces of the magnet |83 and with the con tact 22i in engagement with the contact 265, whereas in Figure 5 the armature is shown separated from the pole faces of the magnet |33 to maximum gap position and with the contact 22| in engagement with the contact 2&6.

The movement is relatively slight, and the structure described not only holds the armature against the magnet when the coil is energized, but moves the armature from maximum armature gap position to engagement with the magnet by the energization of the coil by the relatively weak electromotive force set up by the heat of the flame on the thermocouple.

The thermocouple S, which has the hot junction 3| and the usual cold junction, may be mounted as shown in Figure l on a bracket or other suitable support 26|? by means of a tubular nut 2'2 having threaded engagement with the bracket or support 26u, and cooperating with the tapered surface of an enlargement 2663 on the thermocouple.

The outer exposed surfaces of the insulating terminal blocks 299 (Figure l) may be differently colored or differently marked at the respective contacts to facilitate proper connection ci the respective conductors therewith. In the case of coloring, the outer face of the insulation at one contact may be colored red, the outer I'ace of the corresponding insulating member at another contact may be colored blue, and the outer exposed face of the insulating member at the third contact means may be colored white. Any other different colorings or other suitable markings may, oi course, be employed.

l do not intend to be limited to the precise details shown or described.

I claim:

l. In a device of the character described, an electromagnet comprising a frame having pole ends, a leaf spring supported at one end for movement toward and away from the pole ends of said frame, an armature carried by said spring remote from said one end thereof fulcrumed at one edge on said pole ends for rocking movement toward and away from the latter and having limited movement away from said pole ends, said spring urging said amature away from said pole ends, and means cooperating with said spring for adjusting said end thereof toward and away from said pole en'ds and thereby varying the tension of said spring effective for urging said armature away from said pole ends.

2. In a device of the character described, an el'ectromagnet comprising a frame having pole ends. a leaf spring supported at one end for movement toward and away from the pole ends oi' said frame, an armature carried by said spring remote from said one end thereof fulcrumed at one edge on said pole ends for rocking movement toward and away from the latter and having limited movement away from said pole ends, and an abutment member contacting the face of said springaway from said pole ends, said abutment member being adjustable for varying the tension of said spring effective for urging said amature away from said pole ends.

3. In a device of the character described, a supporting structure comprising two opposite walls, an electromagnet mounted on one of said walls and extending inward therefrom toward the other wall, said electromagnet comprising a frame having pole ends facing toward said other wall, a leaf spring extending downward below said pole ends adjacent said other wall, means carried by said other wall adjacent the lower end of said spring loosely supporting the latter for movement toward and away from said other wall, an armature carried by said spring at the upper portion thereof fulcrumed at its lower edge on said pole ends for rocking toward and away from the latter and having limited movement away from said pole ends, and an abutment member carried by said other wall contacting the outer face oi' said spring adjacent the lower end thereof, said abutment v.member being adjustable for varying the tension THEODORE A. WETZEL. 

